Ruby - Design patterns tdc2011

Design Patterns + Ruby

@rs_felix http://github.com/fellix http://www.crafters.com.br @crafterstudiohttp://blog.rollingwithcode.com

Por que Ruby?

Erich Gamma, Richard Helm,Raph Johnson, John Vlissides

“Gang of Four”

Design Patterns

Template Method

class Relatorio def generate output_head output_body output_footer end def output_head end def output_body end def output_footer endend

class Relatorio def generate output_head Template output_body Method output_footer end def output_head end def output_body end def output_footer endend

class HTMLRelatorio < Relatorio def output_head puts "<html><head> <title>Relatório HTML</title> </head>" end def output_body puts "<body>...</body>" end def output_footer puts "</html>" endend

relatorio = HTMLRelatorio.newrelatorio.generate

class Relatorio def generaterelatorio = HTMLRelatorio.new output_headrelatorio.generate output_body output_footer end end

<html> <head><title>...</title></head> relatorio = HTMLRelatorio.new <body> relatorio.generate ... </body></html>

Strategy

Delegar ao invés de herdar

class Formatter def format(text) endend

class Formatter def format(text) raise "Abstract method" endend

class HTMLFormatter < Formatter def format(text) puts "<html> " puts "<head> " puts "<title>...</title></head> " puts "<body>#{text}</body></html>" endend

class HTMLFormatter def format(text) puts "<html> " puts "<head> " puts "<title>...</title></head> " puts "<body>#{text}</body></html>" endend

Duck Typingclass HTMLFormatter def format(text) puts "<html> " puts "<head> " puts "<title>...</title></head> " puts "<body>#{text}</body></html>" endend

class Relatorio def initialize(formatter) @formatter = formatter end def generate(text) @formatter.format(text) endend

class Relatorio def initialize(formatter) @formatter = formatter Delegate end def generate(text) @formatter.format(text) endend

relatorio = Relatorio.new(HTMLFormatter.new)relatorio.generate("Muitas e muitas coisas")

Observer

Manter-se informado sobre determinadas mudanças em objetos

class NotaFiscal def pagar ... endend

class FluxoCaixa def atualizar ... endend

Consulta no bancoclass FluxoCaixa de dados todas as def atualizar notas pagas e ... atualiza o ﬂuxo de end caixaend

pagarNotaFiscal FluxoCaixa

class NotaFiscal def pagar ... endend

class NotaFiscal def pagar (ﬂuxo) ... ﬂuxo.atualizar endend

class NotaFiscal def initialize (...) ... @observers = [] end def pagar ... endend

class NotaFiscal def add_observer (observer) @observers << observer end def notify_observers @observers.each do |o| o.update(self) end endend

class FluxoCaixa def atualizar ... end def update (nota_ﬁscal) ... endend

fluxo_caixa = FluxoCaixa.newnota_fiscal = NotaFiscal.newnota_fiscal.add_observer fluxo_caixanota_fiscal.pagar

require "observer"class NotaFiscal include Observable def pagar ... changed notify_observers(self) endend

require "observer"class NotaFiscal include Observable def pagar @changed = true ... changed notify_observers(self) endend

require "observer" class NotaFiscal include Observable@observers.each { pagar def |o| o.update(object) } if @changed ... changed notify_observers(self) end end

class FluxoCaixa def atualizar ... end def update (nota_ﬁscal) ... endend

fluxo_caixa = FluxoCaixa.newnota_fiscal = NotaFiscal.newnota_fiscal.add_observer fluxo_caixanota_fiscal.pagar

notificanota_fiscal fluxo_caixa = FluxoCaixa.new fluxo_caixa nota_fiscal = NotaFiscal.new nota_fiscal.add_observer fluxo_caixa nota_fiscal.pagar

Factory

Fornecer uma interface para a criação de objetos, sem especiﬁcar a classe concreta

HTMLReader.new

PDFReader.new

class ReaderFactory def initialize (format) @reader_class = self.class.const_get("#{format}Reader") end def reader @reader_class.new endend

html_reader = ReaderFactory.new("HTML").reader

pdf_reader = ReaderFactory.new("PDF").reader

class ReaderFactory def self.pdf_reader ReaderFactory.new("PDF").reader end def self.html_reader ReaderFactory.new("HTML").reader endend

html_reader = ReaderFactory.html_reader

Active Record Factory

class Base ...end

class Base def self.mysql_connection ... endend

class Base def self.postgresql_connection ... endend

adapter = "mysql"method_name = "#{adapter}_connection"Base.send(method_name, conﬁg)

Builder

Criar objetos complexos de forma legível, passo a passo

class Pizza attr_accessor :massa, :molho, :coberturaend

class PizzaBuilder attr_reader :pizza def initialize @pizza = Pizza.new endend

class CalabresaBuilder < PizzaBuilder def molho @pizza.molho = "Tomate" end def massa @pizza.massa = "Pão" end def cobertura @pizza.cobertura = "queijo, calabresa" endend

builder = CalabresaBuilder.newbuilder.molhobuilder.coberturabuilder.massapizza = builder.pizza

pizza = CalabresaBuilder.new .molho .cobertura .massa .pizza

class CalabresaBuilder < PizzaBuilder def molho @pizza.molho = "Tomate" self end def massa @pizza.massa = "Pão" self end def cobertura @pizza.cobertura = "queijo, calabresa" self endend

builder = CalabresaBuilder.newbuilder.molho_and_coberturapizza = builder.pizza

class PizzaBuilder def method_missing(name, *args) methods = name.to_s.split("_") return super(name, *args) unless methods[1] == "and" methods.each do |method| next if method == "and" send(method) end endend

builder.molho_and_cobertura

builder.massa_and_cobertura

builder.molho_and_cobertura_and_massa

Adapter

Conectar objetos que não tem uma interface comum

class Padrao1 def conectar (cabo) cabo.energizar endend

class CaboPadrao1 def energizar ... endend

class Padrao2 def conectar (cabo) cabo.executar endend

class CaboPadrao2 def executar ... endend

class CaboPadrao2 def executar tomada = Padrao2.new ... tomada.conectar end CaboPadrao2.newend

class CaboPadrao2 def executar tomada = Padrao1.new ... tomada.conectar end CaboPadrao2.newend

class AdapterPadrao2 def initialize(cabo_padrao2) @cabo = cabo_padrao2 end def energizar @cabo.executar endend

adapter = AdapterPadrao2.new(CaboPadrao2.new)tomada = Padrao1.newtomada.conectar(adapter)

tomada adapter caboadapter = AdapterPadrao2.new(CaboPadrao2.new)tomada = Padrao1.newtomada.conectar(adapter)

class ContaBancaria def initialize(saldo) @saldo = saldo end def depositar!(valor) @saldo += valor end def sacar!(valor) @saldo -= valor end def some_method endend

class ContaBancariaProxy def initialize(conta_bancaria) @conta_bancaria = conta_bancaria end def depositar!(valor) @conta_bancaria.depositar! valor end def sacar!(valor) @conta_bancaria .sacar! valor endend

Protection Proxy

class ContaBancariaProxy def initialize(conta_bancaria) @conta_bancaria = conta_bancaria end def depositar!(valor) @conta_bancaria.depositar! valor end def sacar!(valor) @conta_bancaria .sacar! valor endend

class ContaBancariaProxy def initialize(conta_bancaria, owner) @conta_bancaria = conta_bancaria @owner = owner end protected def check_access raise "Illegal Access" unless User. login == @owner endend

class ContaBancariaProxy def depositar!(valor) check_access @conta_bancaria.depositar! valor end def sacar!(valor) check_access @conta_bancaria .sacar! valor endend

Decorator

class Coffee def price @price end def ingredients @ingredients endend

class MilkDecorator def initialize (coffee) @coffee = coffee end def price coffee.price + 0.5 end def ingredients coffee.ingredients + ", Leite" endend

coffee = Coffee.new(1.5, "Café, Água")puts coffee.ingredients

coffee = Coffee.new(1.5, "Café, Água")puts coffee.ingredients Café, Água

coffee = Coffee.new(1.5, "Café, Água")coffee = MilkDecorator.new coffeeputs coffee.ingredientsputs coffee.price

coffee = Coffee.new(1.5, "Café, Água")coffee = MilkDecorator.new coffeeputs coffee.ingredients Café, Água, Leiteputs coffee.price

coffee = Coffee.new(1.5, "Café, Água")coffee = MilkDecorator.new coffeeputs coffee.ingredientsputs coffee.price 2.0

class ChocolateDecorator def initialize (coffee) @coffee = coffee end def price coffee.price + 1.0 end def ingredients coffee.ingredients + ", Chocolate" endend

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffeeputs coffee.ingredients

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffee Café, Água,puts coffee.ingredients Chocolate

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffeeputs coffee.ingredients

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffee

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffeecoffee = MilkDecorator.new coffee

coffee = Coffee.new(1.5, "Café, Água")coffee = ChocolateDecorator.new coffeecoffee = MilkDecorator.new coffee Café, Água,puts coffee.ingredients Chocolate, Leite

Singleton

Garantir que só haja uma instancia de determinado objeto

@count

@count@@count

class CountTester @@count = 0 def initialize @count = 0 end def self.increment @@count++ end def increment @count++ endend

class CountTester Variável @@count = 0 Global def initialize @count = 0 end def self.increment @@count++ end def increment @count++ endend

class CountTester @@count = 0 def initialize Variável @count = 0 Local end def self.increment @@count++ end def increment @count++ endend

class CountTester @@count = 0 def initialize @count = 0 end Metódo def self.increment Estático @@count++ end def increment @count++ endend

class CountTester @@count = 0 def initialize @count = 0 end def self.increment @@count++ end Metódo de def increment Instância @count++ endend

class CountTester Variável COUNT = 0 Globalend

class Logger @@instance = Logger.new def self.instance @@instance endend

logger1 = Logger.instancelogger2 = Logger.instance

logger = Logger.new

class Logger @@instance = Logger.new def self.instance @@instance endend

class Logger @@instance = Logger.new def self.instance @@instance end private_class_method :newend

require "singleton"class Logger include Singletonend

logger = Logger.new

logger = Logger.new private method ‘new’ called for Logger::Class

logger = Logger.instance

Obrigado @rs_felix http://github.com/fellix http://www.crafters.com.br @crafterstudiohttp://blog.rollingwithcode.com

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Ruby - Design patterns tdc2011

by Rafael Felix da Silva on Aug 22, 2011

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Ruby - Design patterns tdc2011 — Presentation Transcript